1. Field of Invention
The present disclosure relates to a process for obtaining valuable products from carbonaceous feedstock.
2. Discussion of Related Art
Due to the dwindling petroleum resources, in recent years there has been an increased demand for recovery of hydrocarbonaceous compounds from non-volatile carbonaceous matter such as coal, biomass, lignite, municipal solid waste and other carbon-containing wastes, as an alternative method for obtaining petrochemical compounds. A pyrolysis or heat treatment is commonly used by which the carbonaceous matter is decomposed into the hydrocarbon products. When coal is pyrolyzed at a high temperature it undergoes destructive pyrolysis and is converted to liquid and light gaseous hydrocarbonaceous fluids and char. A major problem associated with this process is the low efficiency. Further, it is difficult to manipulate the contact time/residence time in the pyrolysis zone, which is an important factor for deciding the efficiency of the process. Still further, the pyrolysis process requires very short reaction time; therefore, it is very necessary to provide uniform heat distribution through the carbonaceous feed during the reaction time to get optimum yield.
Several attempts have been made in the past to provide processes for obtaining hydrocarbon products from carbonaceous feedstock. Some of the disclosures are listed in the prior art below:
U.S. Pat. No. 3,855,070 discloses a process for hydropyrolyzing a solid or liquid hydrocarbonaceous fuel comprising charging the fuel to a fluidized bed having a bed of coke pellets fluidized with a gas containing hydrogen and operating at a temperature of 1100-1800° F. and pressure greater than 20 atm; wherein the solid products of the hydropyrolysis accrete upon the coke pellets and the gaseous products are collected in a space above the fluidized bed. The process aims at providing an improved method for supplying heat to (or removing heat from) a fluidized bed zone in which coal or oil is pyrolyzed.
U.S. Pat. No. 4,210,492 discloses a process for pyrolysis of coal, characterized by efficient water removal and heat transfer, wherein subdivided coal is preheated, pyrolyzed, and subjected to heat recovery after pyrolysis; the heat transfer being effected by contacting the subdivided coal as a dilute-phase fluidized bed in a first stage of dual preheating zones with a first particulate heat carrier, with a second particulate heat carrier in a dense fluidized bed in a second preheating stage, followed by pyrolysis in a dense fluidized bed pyrolysis zone.
The processes for pyrolyzing carbonaceous feed disclosed in the prior art above are complex, have multiple stages, are operated under very high pressures, and do not overcome all the above-listed drawbacks of the pyrolysis process. Therefore, there is felt a need for an improved process for pyrolyzing carbonaceous material which is simple, single-stage and overcomes the drawbacks of the known processes.